Here is the full list of all 33 Runner3 achievements.
Got 'em All!
Go exploring in the Retro World. Maybe you'll find a cute secret?
Better out than in...
Unlock EVERYTHING!
Buy a bunch of new digs!
Buy a bunch of Accessories!
Buy a bunch of Capes!
Bonk the Timbletot!
Defeat Machineland's Boss!
Get all the Gildans!
Defeat the Jungle Ruins' Boss!
Get all your friends over for some GRILLINS!
Collect all the Narrator's Puppetshow Puppets!
Witness something creepy.
Finish all 9 Impossible Levels!
Defeat Spookyland's Bosses!
Head off the Beaten Path...
Defeat The Caves' Bosses!
Defeat Foodland's Boss!
Defeat The Great Outdoors' Boss!
Invite a friend to the BBQ!
Get a Special in each Standard Level in any World!
Get a Perfect in each Standard Level in any World!
Make it to the end of an Impossible Level!
Collect all Golds and Gems and finish an Impossible Level!
Checkpoints? Who needs 'em!
Get a Special AND a Perfect in any one level!
Get a Special, a Perfect, and one Bullseye in any Level!
Get a Special+ and a Perfect+ in any Level!
Get a Perfect!
Get a Perfect+!
Get a Special!
Get a Special+!